Study On Nitrogen Removal Performance Of Immobilized Anammox Sludge

The pivotal role of anammox in the realm of biological nitrogen elimination necessitates the cultivation of anaerobic anammox bacteria,serving as the cornerstone in achieving the process’s effective and unwavering execution.However,the combination of immobilization technology and anammox process can effectively improve the problems existing in practical application,such as easy loss of biomass and difficult to guarantee the removal effect,and finally realize the stability and improvement of nitrogen removal efficiency.The main contents of the test are as follows:The performance indexes of different materials embedded and fixed anammox bacteria were compared.Single factor and orthogonal tests were used to determine the optimal ratio of the selected materials,and the gel spheres were characterized under these conditions.The effects of environmental factors on the denitrification performance of gel pellets were investigated.Finally,under the condition of continuous water inlet,the operation status of anaerobic reactors containing gel spheres and unfixed bacteria was studied,and the changes of anaerobic ammoxidation activity,morphological structure and other aspects of corresponding sludge were comprehensively analyzed.The main work was as follows:（1）Three kinds of immobilized gel spheres,namely PVA,PVA-CS and PVA-CS-Fe,were prepared,and the physicochemical properties of the three spheres were analyzed.The mass transfer coefficients of ammonia nitrogen of the corresponding gel spheres were 0.545×10^-9m²/s,0.685×10^-9m²/s and 0.707×10^-9m²/s,respectively.The removal rate of ammonia nitrogen of unembedded bacteria and three kinds of gel spheres can reach more than 90%,and the removal rate of nitrous nitrogen is more than 82%.The anaerobic ammoxidation activity of the PVA-CS-Fe gel ball was slightly higher than that of the PVA-CS gel ball,but the mechanical strength and physical stability of the PVA-CS gel ball were slightly lower than that of the PVA-CS gel ball,and the performance of the PVA gel ball was poor in these aspects.PVA-CS-Fe and PVA-CS carriers are more likely to form into pellets during the immobilization process,which is non-toxic to organisms and cheap.After comprehensive consideration,PVA-CS-Fe is selected as the embedded carrier to fix anammox bacteria,and the material ratio and nitrogen removal performance are further studied.（2）The results of single factor and orthogonal test showed that the PVA-CS-Fe embedding pellets had the best removal effect on ammonia nitrogen under the conditions of 10%polyvinyl alcohol concentration,1%chitosan concentration,1:2mud inclusion amount and 24h crosslinking time,and the mechanical strength and pellet formation difficulty of the embedding pellets met the requirements.The results of scanning electron microscopy showed that the gel sphere at this time had a complex network structure and obvious pores,indicating that the microorganisms were properly fixed in the gel sphere at this time,and thus improved the anaerobic ammoxidation activity.The influence of reaction conditions on the denitrification efficiency of immobilized anammox bacteria and unembedded bacteria was investigated.It was found that under conditions wherein the temperature reached between 32.5 to 35 degrees Celsius,the p H level measured between 7.5 to 8.0,the initial concentration of NH₄⁺-N rested in the range of one hundred to one hundred and twenty milligrams per litre,and,concurrently,the hydraulic retention time exceeded twelve hours,the following results were observed.,Both the PVA-CS-Fe gel spheres and the free anammox bacteria showed good ammonia removal effect.（3）Under the condition of continuous water intake in the reactor,observed from the whole stage,the denitrification effect of the reactor containing immobilized anammox bacteria is better.Its nitrogen removal rate and load are basically close to or greater than that of free bacteria,and its impact load resistance is also higher.Upon reaching the culmination of the endeavor,it was observed that the gel had incurred impairment,whereas the tripartite reactors had exhibited proficient rates of 89.42percent,89.81 percent,and 90.26 percent for NH₄⁺-N,and 85.83 percent,87.75percent,and 86.37 percent for NO₂^--N,in a sequential fashion.The terminal amounts of removed nitrogen were recorded at 0.736,0.734,and 0.741 kg·m^-3·d^-1.?NO₂^--N/?NH₄⁺-N and?NO₃^--N/?NH4⁺-N are both around 1.27 and 0.24,close to the theoretical value.（4）At the end of the test,the sludge was red and its settling characteristics were improved to some extent.Upon observation through the application of scanning electron microscopy（SEM）,it was determined that there was a noticeable and noteworthy augmentation of the density of globular bacteria.Concurrently,there was a substantial reduction in the count of miscellaneous bacteria present within the samples.It was also determined that there was an evolution in the shape of the sludge particles,with the form becoming much more regular and standardized.Further analysis of microbial community structure revealed that species abundance increased significantly,while community diversity decreased.The phylum’s relative abundance underwent a sharp elevation of proportion,rising from an initial percentage of 24.95%to consecutive percentages of 32.16%,40.74%,and 46.38%,thus demonstrating an unequivocal increase in its prevalence within the studied population.At the genus level,Candidatus Kuenenia increased to 39.86%,44.91%and 53.65%.The results showed that the immobilized carrier could achieve more efficient enrichment of anammox bacteria,so as to further improve the nitrogen removal effect.